High-fat diet promotes exhaustion-associated T-cell remodeling across vascular and lymphoid tissues in atherosclerosis-prone mice

Background: Atherosclerosis is a chronic inflammatory disease driven by lipid accumulation and immune dysregulation. How chronic dietary lipid exposure reshapes T-cell states across vascular and lymphoid tissues, and whether these changes resolve after dietary normalization, remains incompletely defined. This study examined diet-associated T-cell remodeling and the contribution of macrophage-mediated stimulation. Methods: ApoE-deficient mice received a vegetarian diet (VD) or high-fat diet (HFD) for 12 or 24 weeks; a dietary reversal group received HFD for 12 weeks followed by VD for 12 weeks. CD45-positive cells from aorta, blood, spleen, lymph nodes, and bone marrow underwent single-cell RNA sequencing with matched T-cell receptor sequencing. T cell states were annotated using canonical markers, and exhaustion- and naive-associated programs were quantified using UCell scores. Analysis assessed T-cell composition, clonal expansion, and predicted macrophage-T cell communication, with splenic flow-cytometric validation. Results: HFD was associated with enrichment of exhaustion-associated states, with the highest exhaustion scores in the aorta. At 24 weeks, the pooled exhausted-cell proportion was 15.7% under HFD versus 10.6% under VD. Dietary reversal restored this proportion to 10.6%, while residual transcriptional changes persisted in a tissue-dependent manner. Flow cytometry corroborated increased inhibitory receptor expression and co-expression. Aortic macrophages exhibited inflammatory and antigen-presentation programs alongside increased predicted communication with T cells. Aortic T-cell activation and clonal expansion accompanied these changes, and clonotype size correlated with exhaustion score (Spearman correlation coefficient = 0.57, p = 0.029). Conclusion: Chronic HFD is associated with multicompartment T-cell remodeling, with prominent vascular exhaustion-associated programs and tissue-dependent recovery after dietary normalization. These findings suggest that dietary lipid exposure may leave a durable adaptive immune imprint across organs during atherosclerosis.